Now..does anyone know why the number of satellites varies the way it does. Sometimes, my BU-303 can find 5, 8, 9, 11, or 12 satellites. what determines this number?

for clarification it will be like 5/8 used or 9/12...what determines the total number is the question

The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). If you get something like 9/12 I guess it means that in your area are 12 satellites "available" and you are picking 9 of them.

If you get something like 9/12 I guess it means that in your area are 12 satellites "available" and you are picking 9 of them.

Correct, the number of satellite available is determined by your GPS reciever after reviewing the almanac data provided by the other satellites. Each satellite knows where the other satellites are and this information is passed on to your GPS reciever. Most GPS recievers are only 12-channel parallel, which means you won't see any more than 12 satellites simultaneously. I think the most I've seen was 11/12.